Fukushima Unit 2 Containment Inspection, What You Need To Know

IRID released a report late in December, 2016 that outlines in great detail, the technical tasks involved in the upcoming robot containment inspection of unit 2.

Besides gathering data in this area, this work will also help provide data to be used for designing a method to remove the melted fuel (corium).

The robot dubbed Scorpion will be sent in through the CRD hatch with a task of entering the pedestal region below the reactor. Previous scope inspections confirmed a partial failure of the bottom of the reactor vessel.

So far work has taken place that cleaned the area around the CRD hatch and cut a hole in the metal CRD hatch cover. Robots were used to clean the area, pour a layer of cement then lay down sheets of steel plate. After this was completed, the robotic drilling rig was used to connect to the CRD hatch and drill a hole large enough for the next set of equipment. Extra steps were taken to contain any debris or contamination that could leak out.

With this preparation work completed, the steps to conduct the actual inspection will include inserting another scope to check conditions. Then a small debris removal bot will go in to water blast any small debris that could cause problems for the Scorpion robot. After this the Scorpion robot will be deployed inside the pedestal. The goal is to have the Scorpion robot travel along the metal grate platform inside the pedestal.

Concerns remain about the robot’s ability to withstand the high radiation levels inside containment. Levels found years back were 75 Sieverts/hour. Levels inside the pedestal could be much higher. There are also concerns about the ability of the camera to clearly view for navigation. The on board lighting and expected humidity should make most work visible but slightly cloudy in appearance.

The inspection work appears to be scheduled for some time after March 2017.